U.S. patent application number 13/107596 was filed with the patent office on 2012-11-15 for semisubmersible with five-sided columns.
This patent application is currently assigned to Seahorse Equipment Corp.. Invention is credited to Oriol R. Rijken.
Application Number | 20120285361 13/107596 |
Document ID | / |
Family ID | 47140981 |
Filed Date | 2012-11-15 |
United States Patent
Application |
20120285361 |
Kind Code |
A1 |
Rijken; Oriol R. |
November 15, 2012 |
SEMISUBMERSIBLE WITH FIVE-SIDED COLUMNS
Abstract
A semi-submersible vessel comprises pontoons having a generally
five-sided transverse cross section. In the case of a 4-sided
semi-submersible, the columns may be arranged in a generally
rectangular form with a column at each corner of the rectangular
form, each column having with four sides disposed at a right angle
to at least one adjacent side and a fifth side on the exterior of
the generally rectangular form disposed at 45 degrees to each
adjacent side.
Inventors: |
Rijken; Oriol R.; (Houston,
TX) |
Assignee: |
Seahorse Equipment Corp.
Houston
TX
|
Family ID: |
47140981 |
Appl. No.: |
13/107596 |
Filed: |
May 13, 2011 |
Current U.S.
Class: |
114/265 |
Current CPC
Class: |
B63B 1/107 20130101;
B63B 21/50 20130101; B63B 35/4413 20130101; B63B 2001/128
20130101 |
Class at
Publication: |
114/265 |
International
Class: |
B63B 35/44 20060101
B63B035/44; B63B 21/50 20060101 B63B021/50 |
Claims
1. A semi-submersible vessel comprising: four pontoons arranged in
a generally rectangular form; a column at each corner of the
rectangular form, each column having a generally five-sided
transverse cross section with four sides disposed at a right angle
to at least one adjacent side and a fifth side on an outboard face
of the generally rectangular form disposed at 45 degrees to each
adjacent side.
2. A semi-submersible vessel as recited in claim 1 wherein the
ratio of the length of the diagonal of each column's transverse
cross-section that is parallel to the fifth side to the distance
from the mid-point of the fifth side to the opposite corner of the
transverse cross-section is greater than or equal to 4/3.
3. A semi-submersible vessel as recited in claim 1 further
comprising at least one anchor line attached to the fifth side of
at least one column.
4. A semi-submersible vessel as recited in claim 3 wherein the
anchor line is attached to the column by means of a fairlead
proximate the bottom of the column.
5. A semi-submersible vessel as recited in claim 3 wherein the
anchor line is attached to the column by means of a fairlead
proximate the bottom of the column and a winch proximate the top of
the column.
6. A semi-submersible vessel as recited in claim 5 further
comprising a chain stop configured to engage the anchor line.
7. A semi-submersible vessel as recited in claim 4 wherein the
anchor line is routed along the fifth side of the column.
8. A surface-piercing column of a buoyancy-supported structure
wherein the aspect ratio of the transverse cross section of the
column is at least 4:3 and wherein the geometric center of the
cross section is located closer to the interior of the
buoyancy-supported structure than the geometric center of the
smallest circle that completely inscribes the cross section of the
column.
9. A semisubmersible vessel comprising: a plurality of pontoons
arranged generally in the form of a regular polygon having n sides;
a column at each vertex of the polygonal form, each column having a
generally five-sided transverse cross section with at least three
sides disposed at a right angle to at least one adjacent side and
two adjacent sides having pontoons attached thereto disposed at an
angle of 360/n degrees to one another.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] None
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] This invention relates to floating vessels. More
particularly, it relates to platform-type semisubmersible
vessels
[0005] 2. Description of the Related Art Including Information
Disclosed Under 37 CFR 1.97 and 1.98
[0006] A semi-submersible is a particular type of floating vessel
that is supported primarily on large pontoon-like structures
submerged below the sea surface. The operating decks are typically
elevated about 100 or more feet above the pontoons on steel
columns. This design has the advantage of submerging most of the
area of the components in contact with the sea and minimizing
loading from waves and wind. Semisubmersibles can operate in a wide
range of water depths, including deep water. They are usually
anchored with six to twelve anchors tethered by chains and/or wire
cables, which are computer controlled to maintain stationkeeping.
Semi-submersibles (or "semis") can be used for drilling, workover
operations, and production platforms, depending on the equipment
with which they are equipped. When fitted with a drilling package,
they may be called semisubmersible drilling rigs.
[0007] As shown in FIG. 1, a semi-submersible hull 100 of the prior
art commonly has columns 102 at the corners of the vessel that are
rectangular in cross section. Each column is attached to two
pontoons 104 which extend between adjacent columns. Central opening
106 is defined by pontoons 104. Typically, a deck (not shown) is
support on upper surface 108 of columns 102.
[0008] Certain semi-submersibles of the prior art have columns that
are rectangular (four faces per column) and are positioned such
that the column faces (sides) are set at 45 degrees with respect to
the longitudinal axis of the adjoining pontoon.
[0009] The column shape of the present invention is similar to that
of the "EXMAR OPTI-EX" semi-submersible illustrated in FIG. 2.
However, in the case of that semi-submersible, the non-orthogonal
fifth-face of each column is oriented towards the interior of the
semi-submersible rather than the exterior.
BRIEF SUMMARY OF THE INVENTION
[0010] The present invention relates to the shape of each of the
columns on a semi submersible. In a 4-column semi-submersible
according to the invention, each of the four columns has five
faces, four of the five faces are perpendicular to at least one
adjacent face. The fifth face is the outermost face of the column.
The angle between the fifth face and the longitudinal axis of an
adjacent pontoon is preferably about 45 degrees.
[0011] The column configuration of the invention is a variant of
the existing deep draft semi submersible configuration used for the
dry tree semi submersible vessels Independence Hub and Thunder Hawk
which operate in the Gulf of Mexico.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0012] FIG. 1 is a dimensioned perspective drawing of a
semi-submersible hull of the prior art having rectangular
columns.
[0013] FIG. 2 contains perspective views from above and below of a
semi-submersible vessel of the prior art having 5-sided
columns.
[0014] FIG. 3 is a top plan view of a five-sided column
semisubmersible according to one embodiment of the invention.
[0015] FIG. 4 is a perspective view of a semisubmersible having
five-sided columns according to an embodiment of the invention.
[0016] FIG. 5 is a cross-sectional view of a 5-sided
semi-submersible column according to one embodiment of the
invention.
[0017] FIG. 6 is a is a cross-sectional view of a 5-sided
semi-submersible column according to another embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The invention may best be understood by reference to certain
illustrative embodiments which are shown in the drawing
figures.
[0019] Referring now to FIG. 3, a hull 300 of a 4-column, 4-pontoon
semi-submersible according to one embodiment of the invention is
equipped with 5-sided columns 302 at the corners of the vessel. It
will be noted that each of the four columns 302 has five faces,
four of the five faces (312, 312', 314 and 314') are perpendicular
to at least one adjacent face. The fifth face 310 is the outermost
face of the column. The angle between the fifth face 310 and the
longitudinal axis of an adjacent pontoon 304 in the illustrated
embodiment is 45 degrees. Central opening 306 in hull 300 is
bounded by columns 302 and pontoons 304.
[0020] FIG. 4 shows a semi-submersible 400 having a hull comprised
of columns 402 and pontoons 404 which together define central
opening 406. Semi-submersible 400 has a hull according to the form
illustrated in FIG. 3. Deck 420 is supported on columns 402 and may
include helipad 422, flare boom 424, crane 426 and process
equipment 428. Anchor lines 430 may be routed through fairleads 434
on the outboard face of each column 402 to winches 436. The upper
end of risers 432 are supported on pontoons 404.
[0021] As may be seen in FIG. 4 the corners of columns 402--i.e.,
the junctures of adjacent sides--may be rounded. Such rounded
corners may improve the hydrodynamic properties of the vessel.
[0022] In the embodiment illustrated in FIG. 3, each of columns 302
has five sides--sides 314 and 314' are of equal length and
orthogonal to each other and each is attached to an adjacent
pontoon 304. Shorter sides 312 and 312' are of equal length and are
orthogonal to sides 314 and 314', respectively. Fifth, outboard
side 310 is joined to both sides 312 and 312' at a 45-degree angle.
In the particular embodiment illustrated in FIG. 3, pontoons 304
are centered on sides 314. However, in other embodiments, the
centerline of pontoon 304 may be inboard or outboard of the center
of column side 314.
[0023] The ratio of the length of the diagonal that is parallel to
the non-orthogonal face to the distance from the mid-point of the
non-orthogonal face to the opposite corner is preferably greater
than or equal to 4/3. Stated another way, the geometric center of a
column's cross section should be inboard of the center of a circle
which circumscribes the cross section. This configuration is
illustrated graphically in FIG. 5 wherein column 502 has five
sides--sides 514 and 514' are of equal length and orthogonal to
each other and each may be attached to an adjacent pontoon (not
shown). Shorter sides 512 and 612' are of equal length and are
orthogonal to sides 514 and 614', respectively. Fifth,
non-orthogonal side 510 is joined to both sides 512 and 512' at a
45-degree angle. Preferably, the length of sides 512 is chosen such
that D1/D2.gtoreq.1.33
[0024] The 5-sided column illustrated in FIG. 5 is "square" in
overall planform--i.e., sides 514 and 514' are of equal length.
This, however, need not be the case for each embodiment of the
invention. A "rectangular" 5-sided column according to another
embodiment of the invention is shown in FIG. 6. In this embodiment,
S2>S1. Sides 614 and 614' are adjacent and may be used to attach
column 602 to pontoons (not shown). Shorter sides 612 and 612' join
sides 614 and 614', respectively to outboard side 611. In the
illustrated embodiment, sides 614 and 614' are orthogonal (angle
.alpha. is 90.degree.) and column 602 could be used on a 4-sided
semi-submersible hull. However, it will be appreciated by those
skilled in the art that by varying the length of sides 612 and/or
611, angle .alpha. may assume a value other than 90.degree.. For
example, if column 602 were intended for use in a semi-submersible
hull that was a regular pentagon in planform, the length of side
611, 612 and/or 614 may be selected such that angle
.alpha.=72.degree..
[0025] A semi-submersible equipped with the column form disclosed
herein has at least two advantages: [0026] the mooring lines can
connect to the hull at a right angle which allows for an easier
load distribution into the column (no shear) [0027] The mooring
chain does not have to twist between the fairlead and the windlass
or chain jack which makes installation less prone to
complications
[0028] A column form according to the present invention may provide
an advantage in the vortex-induced motion (VIM) response of the
vessel.
[0029] VIM amplitudes are the highest at a current heading along
the platform diagonal. VIM amplitudes are minimal when the current
is perpendicular to the column face (four-faced column). A key
parameter in VIM response is the projected width of the column onto
a plane perpendicular to the current. Each column has the same
projected width for a semi submersible having columns of
rectangular cross section. A configuration according to the present
invention has two distinct widths for each current heading
(different from perpendicular). The different widths result in a
configuration where two of the columns are in full lock-in and two
columns are not in full lock-in, and thus a reduction in VIM
amplitudes may be achieved.
[0030] If the aspect ratio of the column (along the diagonal) is
approximately 3:4, only a 6% increase in column width is necessary
to maintain the buoyancy contribution of the column (as compared to
a conventional column of rectangular cross section).
[0031] Although the invention has been described in detail with
reference to certain preferred embodiments, variations and
modifications exist within the scope and spirit of the invention as
described and defined in the following claims.
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